U.S. patent number 7,075,306 [Application Number 11/228,195] was granted by the patent office on 2006-07-11 for power control unit.
This patent grant is currently assigned to Hitachi, Ltd.. Invention is credited to Akihiko Emori, Takuya Kinoshita, Tsutomu Miyauchi, Hideki Miyazaki, Motomi Shimada, Masato Suzuki, Eiichi Toyota.
United States Patent |
7,075,306 |
Emori , et al. |
July 11, 2006 |
Power control unit
Abstract
A power control apparatus for controlling charging and
discharging of a plurality of storage means devices has a voltage
measuring arrangement for measuring voltages of each of the storage
devices, a current measuring arrangement for measuring currents
flowing through each of the storage devices, a status detector for
detecting the operating status of each storage device from values
measured by the voltage and current measuring arrangements, and a
charging/discharging control device for controlling currents,
voltages, or power according to the operating status of each
storage devices detected by the status detector to charge or
discharge the storage devices.
Inventors: |
Emori; Akihiko (Hitachi,
JP), Toyota; Eiichi (Hitachinaka, JP),
Suzuki; Masato (Urizura-machi, JP), Shimada;
Motomi (Hitachinaka, JP), Miyauchi; Tsutomu
(Hitachi, JP), Kinoshita; Takuya (Yokosuka,
JP), Miyazaki; Hideki (Hitachi, JP) |
Assignee: |
Hitachi, Ltd. (Tokyo,
JP)
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Family
ID: |
32708849 |
Appl.
No.: |
11/228,195 |
Filed: |
September 19, 2005 |
Prior Publication Data
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Document
Identifier |
Publication Date |
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US 20060012372 A1 |
Jan 19, 2006 |
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Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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10751905 |
Jan 7, 2004 |
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Foreign Application Priority Data
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Jan 8, 2003 [JP] |
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2003-002153 |
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Current U.S.
Class: |
324/430; 324/426;
320/106 |
Current CPC
Class: |
H02J
7/0022 (20130101); H02J 7/0021 (20130101); H02J
7/0013 (20130101); H02J 7/0016 (20130101); H02J
7/0048 (20200101); Y02T 30/00 (20130101); G01R
31/389 (20190101); Y02T 10/70 (20130101) |
Current International
Class: |
G01N
27/416 (20060101); H02J 7/00 (20060101) |
Field of
Search: |
;324/413,405,403,87,382,410,678,426-428,430-434,522
;320/103,104,119,126,132,134,136,149,106 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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08-088944 |
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Apr 1996 |
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JP |
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2001-185228 |
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Jul 2001 |
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JP |
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2002-142353 |
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May 2002 |
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JP |
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Primary Examiner: Nguyen; Vincent Q.
Assistant Examiner: Nguyen; Hoai-An D.
Attorney, Agent or Firm: Crowell & Moring LLP
Claims
The invention claimed is:
1. A power control apparatus for controlling charging and
discharging of a plurality of storage means, said power control
apparatus comprising: voltage measuring means for measuring
voltages of each of said storage means: current measuring means for
measuring currents flowing through each of said storage means; a
status detecting means for detecting an operating status of each
storage means, from values measured by said voltage measuring and
current measuring means; and a charging/discharging controlling
means for controlling currents, voltages, or power according to the
operating status of each storage means detected by said status
detecting means, to charge or discharge said storage means;
wherein: said status detecting means calculates an internal
impedance or open circuit voltage of each storage means; and said
charging/discharging controlling means calculates a permissible
charging or discharging current value of each storage means from
its internal impedance, open circuit voltage, preset maximum
permissible voltage and minimum permissible voltage, calculates a
sum of all currents flowing through said storage means to suppress
a current over the calculated permissible charging or discharging
current from flowing into or out of each of said storage means, and
controls the charging or discharging current to maintain the total
current below the calculated total current value.
2. The power control apparatus of claim 1, wherein said storage
means comprises a device selected from the group consisting of a
lithium secondary cell, a nickel metal-hydride battery, a lead-acid
battery, and an electric double layer capacitor.
3. The power control apparatus of claim 1, wherein said storage
means supplies power to an electric motor which drives vehicle
wheels, and is charged by power generated by a dynamo-electric
generator that is driven by an internal combustion engine on a
vehicle or power from said electric motor when said motor is used
as a power generator.
4. The power control apparatus of claim 1, wherein said status
detecting means calculates the charging status of each storage
means and determines a maximum or minimum of the calculated
charging states; and said charging/discharging controlling means
controls the charging current, voltage, or power by the maximum
charging status value and controls the discharging current,
voltage, or power by the minimum charging status value.
5. The power control apparatus of claim 1, wherein: said power
control apparatus further comprises a switch which selectively
breaks or makes a connection between said charging/discharging
controlling means and any storage means; and said
charging/discharging controlling means checks the on/off status of
said switch and controls the current, voltage or power according to
the detected on/off status of said switch and the running status of
each storage means to discharge or charge the storage means.
6. The power control apparatus of claim 5, wherein: said status
detecting means calculates the internal impedance or open circuit
voltage of each storage means; and said charging/discharging
controlling means controls charging/discharging currents, voltages,
or power of said storage means according to the impedances or open
circuit voltages thereof.
7. The power control apparatus of claim 5, wherein: said status
detecting means calculates the charging status of each storage
means and determines the maximum or minimum of the calculated
charging states; and said charging/discharging controlling means
controls the charging current, voltage, or power by the maximum
charging status value and controls the discharging current,
voltage, or power by the minimum charging status value.
8. The power control apparatus of claim 1, further comprising: a
load; and a power source selected from the group consisting of a
commercial power supply, a solar energy generator, a micro gas
turbine generator and a fuel cell, to supply power to said loads;
wherein said power control apparatus supplies power to said load or
said commercial power supply and uses power from said power
source.
9. The power control apparatus of claim 1, wherein said storage
means supplies power to an electric motor which drives vehicle
wheels, and is charged by power from outside of a vehicle or power
from said electric motor when said motor is used as a power
generator.
10. A power control apparatus for controlling charging of a
plurality of storage means, said power control apparatus
comprising: voltage measuring means for measuring voltages of each
of said storage means; current measuring means for measuring
currents flowing through each of said storage means; a status
detecting means for respectively calculating internal impedances
and open circuit voltages of each of said storage means, from
values measured by said voltage and current measuring means; and a
charging current controlling means which calculates a permissible
charging current value of each storage means from its internal
impedance or open circuit voltage and a preset maximum permissible
charging voltage which are detected by said status detecting means,
calculates a sum of all currents flowing through said storage means
to suppress a current over the calculated current from flowing into
said storage means, and controls the charging current to maintain
the total current below the calculated total current value.
11. The power control apparatus of claim 10, wherein said storage
means comprises a device selected from the group consisting of a
lithium secondary cell, a nickel metal-hydride battery, a lead-acid
battery, and an electric double layer capacitor.
12. A power control apparatus for controlling discharging of a
plurality of storage means, said power control apparatus
comprising: voltage measuring means for measuring voltages of each
of said storage means; current measuring means for measuring
currents flowing through each of said storage means; a status
detecting means for calculating internal impedances and open
circuit voltages of said storage means, from values measured by
said voltage and current measuring means; and a discharging current
controlling means which calculates a permissible discharging
current value of each storage means, from its internal impedance or
open circuit voltage and a preset maximum permissible discharging
voltage which are detected by said status detecting means,
calculates a sum of all currents flowing through said storage means
to suppress a current over the calculated current from flowing from
said storage means, and controls the discharging current to
maintain the total current below the calculated total discharging
current value.
13. The power control apparatus of claim 12, wherein said storage
means comprises a device selected from the group consisting of a
lithium secondary cell, a nickel metal-hydride battery, a lead-acid
battery, and an electric double layer capacitor.
Description
BACKGROUND OF THE INVENTION
This invention relates to power control apparatus which controls
charging and discharging of a power-generating or rechargeable
power supply such as a fuel cell, lithium secondary cell, nickel
metal-hydride battery, lead-acid battery, and electric double layer
capacitor.
When a plurality of storage means such as batteries are connected
in parallel, series, or both or when a plurality of storage means
of different types are connected in parallel, series, or both,
currents flowing through the storage means are dependent upon
voltages and impedances of the storage means.
Therefore, when the storage means which are connected in parallel,
series, or both are charged or discharged at a time, the current or
voltage value of a certain storage means may exceed a permissible
value.
To solve such a fault, prior arts have employed a method of
controlling charging or discharging of the storage means with the
minimum of currents that can flow through the storage means instead
of charging or discharging with a total of currents that flow
through all parallel-connected storage means (n pieces).
Japanese Application Patent Laid-Open Publication No. 2002-142353
discloses a method of disconnecting a faulty storage means when its
current or voltage goes above a permissible value.
FIG. 9 shows a conventional method of controlling charging and
discharging storage means. In FIG. 9, two or more sets 7 of
series-connected batteries 1 are connected in parallel. Each set 7
of series-connected batteries 1 further comprises a means 9 for
detecting a fault such as a micro short-circuit of each battery 1,
a current bypass circuit 3 which comprises a current control means
(switch) 4 and a resistor 5 and is connected to the battery set 7
in parallel with the set 7, and a fuse 6 which is connected in
series to the bypass circuit 3 and the battery set 1 to
electrically shut off the circuit when an overcurrent takes
place.
When faults such as a micro short-circuit occur in a battery 1, it
is detected by its voltmeter 2. The fault detecting means 9
receives a signal from the voltmeter 2 and closes the switch 4 to
flow a large current through the current bypass circuit 3 which is
connected in parallel to the faulty battery 1. This large current
blows off the fuse 6. With this, the faulty battery is disconnected
from the other non-faulty battery sets.
Japanese Application Patent Laid-Open Publication No. 2001-185228
discloses a system comprising two or more parallel-connected
battery modules each of which has two or more secondary batteries
connected in series. A current detecting circuit and a switch are
connected in series to each battery module.
When one of the current detecting circuits detects an abnormal
current value or direction, a control unit opens a switch of the
battery module containing a faulty battery to disconnect the faulty
battery module from the other non-faulty battery modules.
Japanese Application Patent Laid-Open Publication No. 08-88944
discloses a system which connects a plurality of cells each of
which is a secondary battery or a plurality of battery modules each
of which comprises two or more secondary batteries in series,
parallel, or both. This system detects the voltage and the current
of each cell or module and calculates the quantity of charge.
The system selectively charges cells or modules according to the
result of calculation.
SUMMARY OF THE INVENTION
However, the prior arts disclosed by Patent Documents 1 and 2
cannot charge or discharge currents for "n" batteries in a system
having "n" sets of parallel-connected storage means each of which
contains a plurality of series-connected batteries and cannot
increase the input/output (current) further.
This is because a current by a single battery is charged to or
discharged from "n" sets of parallel-connected storage means in
order to avoid charging or discharging by an over-current assuming
that the performances of the batteries are different.
A time period required to charge or discharge "n" sets of
parallel-connected storage means by a single battery is longer by
"n" times than that required to charge or discharge one battery by
a single battery.
Therefore, the conventional methods will be available to apparatus
that do not require quick charging and apparatus that have a
smaller discharging current than the capacity of the storage means
and do not mind the charging/discharging time.
However, power equipment for vehicles, emergency power equipment,
or new rechargeable power supply apparatus for home use require
quick charging and less weight. In other words, it is very
important for such equipment to reduce the capacity relative to the
discharging current. However, it is beyond the ability of the
conventional technologies.
The technologies of Patent Documents 1 and 2 are designed to
disconnect the storage means from the power control circuit only
after the storage means has a trouble instead of controlling
charging and discharging of the storage means to prevent troubles
from occurring in the storage means. It is possible to make the
service life of the storage means longer by controlling charging
and discharging of the storage means to suppress occurrence of
troubles.
Therefore, it has been hoped that a power control apparatus be
actualized that can control charging and discharging of storage
means to suppress occurrence of troubles while enabling quick
charging and reduction of the capacity relative to the discharging
current.
On the other hand, the technology in Patent Document 3 controls to
charge storage means according to the charging quantity of
respective batteries to suppress the occurrence of a trouble in the
storage means.
However, the technology in Patent Document 3 considers neither
quick charging nor reduction of the capacity relative to the
discharging current and cannot accomplish these. Further, this
technology employs a configuration in which each battery is
equipped with a current control circuit and a current control
element. This makes the configuration of the power control
apparatus complicated and heavy. This technology is far from weight
reduction.
Accordingly, an object of the present invention is to provide a
power control apparatus that can control charging and discharging
of storage means to suppress the occurrence of a trouble in the
storage means while accomplishing quick charging and reduction of
battery capacities relative to discharging currents.
To accomplish the above purpose, this invention is configured as
follows:
(1) A power control apparatus for controlling charging and
discharging of a plurality of storage means, comprising voltage
measuring means for measuring voltages of said storage means
respectively, current measuring means for measuring currents
flowing through said storage means respectively, a status detecting
means for detecting the operating status of each storage means from
values measured by said voltage measuring means and said current
measuring means, and a charging/discharging controlling means for
controlling currents, voltages, or power according to the operating
status of each storage means detected by said status detecting
means to charge or discharge said storage means.
(2) In (1) preferably, the status detecting means preferably
calculates the internal impedance or open circuit voltage of each
storage means and the charging/discharging controlling means
controls charging/discharging currents, voltages, or power of said
storage means according to impedances or open circuit voltages
thereof.
(3) In (1) preferably, said status detecting means calculates the
internal impedance or open circuit voltage of each storage means
and said charging/discharging controlling means calculates the
permissible charging or discharging current value of each storage
means from its internal impedance, open circuit voltage, preset
maximum permissible voltage and minimum permissible voltage,
calculates the sum of all currents flowing through said storage
means to suppress a current over the calculated permissible
charging or discharging current from flowing into or out of each of
said storage means and controls the charging or discharging current
to make the total current below the calculated total current
value.
(4) In (1) preferably, said status detecting means calculates the
charging status of each storage means and determines the maximum or
minimum of the calculated charging states, and said
charging/discharging controlling means controls the charging
current, voltage, or power by the maximum charging status value and
controls the discharging current, voltage, or power by the minimum
charging status value.
(5) In (1) preferably, said power control apparatus further
comprises a switch means which selectively breaks or makes a
connection between said charging/discharging controlling means and
any storage means and said charging/discharging controlling means
checks the on/off status of said switch means and controls the
current, voltage or power according to the detected on/off status
of said switch means and the running status of each storage means
to discharge or charge the storage means.
(6) In (5) preferably, said status detecting means calculates the
internal impedance or open circuit voltage of each storage means
and said charging/discharging controlling means controls
charging/discharging currents, voltages, or power of said storage
means according to the impedances or open circuit voltages
thereof.
(7) In (5) preferably, said status detecting means calculates the
charging status of each storage means and determines the maximum or
minimum of the calculated charging states, and said
charging/discharging controlling means controls the charging
current, voltage, or power by the maximum charging status value and
controls the discharging current, voltage, or power by the minimum
charging status value.
(8) In (1) to (7) preferably, said power control apparatus further
comprises a load and a means selected from a group of a commercial
power supply, a solar energy generator, a micro gas turbine
generator and a fuel cell to supply power to said load, wherein
said power control apparatus supplies power to said load or said
commercial power supply and uses power from said commercial power
supply, a solar energy generator, a micro gas turbine generator or
a fuel cell as a charging power.
(9) In (1) to (7) preferably, said storage means supply power to an
electric motor which drives vehicle wheels and are charged by power
from the outside of a vehicle or power from said electric motor
when said motor is used as a power generator.
(10) In (1) to (7) preferably, said storage means supply power to
an electric motor which drives vehicle wheels and are charged by
power generated by a dynamo-electric generator which is driven by
an internal combustion engine on a vehicle or power from said
electric motor when said motor is used as a power generator.
(11) A power control apparatus for controlling charging of a
plurality of storage means comprising voltage measuring means for
measuring voltages of said storage means respectively, current
measuring means for measuring currents flowing through said storage
means respectively, a status detecting means for respectively
calculating the internal impedances and open circuit voltages of
said storage means from values measured by said voltage and current
measuring means, and a charging current controlling means
calculates a permissible charging current value of each storage
means from its internal impedance or open circuit voltage and a
preset maximum permissible charging voltage which are detected by
said status detecting means calculates the sum of all currents
flowing through said storage means to suppress a current over the
calculated current from flowing into said storage means, and
controls the charging current to make the current below the
calculated total current value.
(12) A power control apparatus for controlling discharging of a
plurality of storage means comprising voltage measuring means for
measuring voltages of said storage means respectively, current
measuring means for measuring currents flowing through said storage
means respectively, a status detecting means for respectively
calculating the internal impedances and open circuit voltages of
said storage means from values measured by said voltage and current
measuring means, and a discharging current controlling means
calculates a permissible discharging current value of each storage
means from its internal impedance or open circuit voltage and a
preset maximum permissible discharging voltage which are detected
by said status detecting means calculates the sum of all currents
flowing through said storage means to suppress a cur rent over the
calculated current from flowing from said storage means, and
controls the discharging current to make the current below the
calculated total discharging current value.
In summary, the present invention can provide a power control
apparatus that can control charging and discharging of storage
means to suppress the occurrence of a trouble in the storage means
while accomplishing quick charging and reduction of battery
capacities relative to discharging currents.
This invention is applied to an energy management system of various
storage means such as power generating elements such as fuel cells,
lithium secondary cell, nickel metal-hydride battery, lead-acid
battery, and electric double layer capacitor and systems using
thereof such as power supply equipment, distributed power storage
equipment, electric cars and vehicles, and tracked vehicles.
BRIEF DESCRIPTION OF THE DRAWINGS
The present invention will be understood more fully from the
detailed description given hereinafter and from the accompanying
drawings of the preferred embodiment of the present invention,
which, however, should not be taken to be limitative to the
invention, but are for explanation and understanding only.
In the drawings:
FIG. 1 is a schematic diagram of a power control apparatus which is
the first embodiment of the invention.
FIG. 2 is a functional block diagram of the inside of a
charging/discharging controlling means in accordance with the
embodiment of FIG. 1.
FIG. 3 is a graph for explaining an example of process that the
status detecting means executes.
FIG. 4 is a schematic diagram of a power control apparatus which is
the second embodiment of the invention.
FIG. 5 is a schematic diagram of a power control apparatus which is
the third embodiment of the invention.
FIG. 6 is a schematic diagram of a power control apparatus which is
the fourth embodiment of the invention.
FIG. 7 is a schematic diagram of a power control apparatus which is
the fifth embodiment of the invention.
FIG. 8 is a schematic diagram of a power control apparatus which is
the sixth embodiment of the invention.
FIG. 9 shows a schematic diagram of a conventional power storage
control apparatus.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
Preferred embodiments of the present invention are described below
with reference to the accompanying drawings, in which like
reference numerals represent the same or similar elements.
FIG. 1 is a schematic diagram of a power control apparatus which is
the first embodiment of the invention. This embodiment is an
example of applying the present invention to a power supply
charging/discharging controlling means. In FIG. 1, means 101a and
101b are power storage means. A means 101b is a voltage measuring
means. Means 103a and 103b are current measuring means. A means 104
is a status detecting means and a means 105 is a
charging/discharging controlling means.
A current measuring means 103a is connected in series to a storage
means 101a and a current measuring means 103b is connected in
series to a storage means 101b. The series set of the current
measuring means 103a and the storage means 101a is connected in
parallel with the other series set of the current measuring means
103b and the storage means 101b.
A voltage measuring means 102 is connected in parallel with these
parallel sets of the current measuring means 103 and the storage
means 101. Further, a charging/discharging controlling means 105 is
also connected in parallel with the storage means 101 and current
measuring means 103. This charging/discharging controlling means
105 is connected to a power supply such as a commercial power
supply, a power generator and a fuel cell and to a load such as an
electronic apparatus (which are not shown in the drawing).
The status detecting means 104 receives a measured voltage value
from the voltage measuring means 102 and measured current values
from the current measuring means 103a and 103b, calculates the
resistance and the voltage of each storage means, and sends the
result to the charging/discharging controlling means 105.
The charging/discharging controlling means 105 performs operations
(to be described below) on the status values (resistances,
voltages, and so on) sent from the status detecting means 104 and
controls the charging and discharging currents of the storage means
101a and 101b by the result.
In this case, it is possible to provide a temperature measuring
means, a pressure measuring means, or both (not shown in the
drawing) to measure the status of each storage means 101.
The power storage means 101a and 101b are power-generating or
rechargeable power storage means such as a fuel cell, lithium
secondary cell, nickel metal-hydride battery, lead-acid battery,
and electric double layer capacitor. These storage means are used
singly or plurally in series or in parallel.
The voltage measuring means 102 comprises some electronic parts
such as voltage-dividing resistors, operational amplifiers, and A/D
converters and measure the voltage of each storage means. Although
this embodiment has the voltage measuring means 102 and the status
detecting means 104 separately, part or the whole of the voltage
measuring means 102 can be built in the status detecting means
104.
Each of the current measuring means 103a and 103b consists of a
Hall CT or shunt type current sensor and measures a current flowing
through each storage means 101. Although the first embodiment of
the present invention has the current measuring means 103a and 103b
and the status detecting means 104 separately, part or the whole of
current measuring means 103a and 103b can be built in the status
detecting means 104.
The status detecting means 104 mainly consists of a microcomputer
and a peripheral IC and detects the status (resistances and
voltages) of respective storage means 101a and 101b from the values
sent from the voltage measuring means 102 and current measuring
means 103a and 103b.
Although the first embodiment of the present invention has the
status detecting means 104 and the charging/discharging controlling
means 105 separately, part or the whole of the status detecting
means 104 can be built in the charging/discharging controlling
means 105.
The charging/discharging controlling means 105 mainly consists of a
power converter such as a converter or an inverter and controls a
current, power, or voltage to be supplied or output to the storage
means 101a and 101b.
The currents passing through the storage means 101a and 101b are
dependent upon their impedances Ra and Rb, their open circuit
voltages (or electromotive forces) Ea and Eb, and the I/O currents,
voltages, and power of the charging/discharging controlling means
105.
Therefore, the status detecting means 104 detects the status
quantities of the storage means 101a and 101b such as the
impedances Ra and Rb, their open circuit voltages Ea and Eb, etc.
and sends them to the charging/discharging controlling means 105.
The charging/discharging controlling means 105 controls the I/O
currents, voltages, and power by the status quantities.
For example, let's assume a storage means has an impedance
(internal impedance) of R, an open circuit voltage (excluding a
voltage drop due to the internal impedance) of E, a maximum
permissible voltage of Vmax, and a minimum permissible voltage of
Vmin. Further, let's assume a storage means can use a permissible
charging current Icmax and a permissible discharging current Idmax
safely and maximally in the maximum permissible voltage range. The
charging and discharging currents Icmax and Idmax are calculated by
equations (1) and (2) below. Icmax=(Vmax-E)/R (1) Idmax=(E-Vmin)/R
(2) where Vmax is a maximum rated voltage of the storage means or a
maximum voltage that is defined by the system such as a load
connected thereto. Vmin is a minimum rated voltage of the storage
means or a minimum voltage that is defined by the system such as a
load connected thereto.
FIG. 1 assumes that the open circuit voltages Ea and Eb of the
storage means 101a and 101b are equal to each other as the storage
means 101a and 101b are connected in parallel to each other and
that the charging/discharging controlling means 105 flows a current
Iall to charge and discharge the storage means 101a and 101b. The
currents Ia and Ib which respectively flow through the storage
means 101a and 101b can be expressed by equations (3) and (4) where
Ra and Rb are internal resistances of the storage means 101a and
101b. Ia=Iall.times.Rb/(Ra+Rb) (3) Ib=Iall.times.Ra/(Ra+Rb) (4)
Equations (3) and (4)
The charging/discharging controlling means 105 controls the current
to satisfy Expressions (5) and (6) during charging and satisfy
Expressions (7) and (8) during discharging.
Iall.times.Rb/(Ra+Rb)<(Vmax.times.Ea)/Ra (5)
Iall.times.Ra/(Ra+Rb)<(Vmax-Eb)/Rb (6)
Iall.times.Rb/(Ra+Rb)<(Ea-Vmin)/Ra (7)
Iall.times.Ra/(Ra+Rb)<(Eb-Vmin)/Rb (8)
In other words, for charging, the charging/discharging controlling
means 105 controls the current to be below the less of
{(Vmax-Ea)(Ra+Rb)/RaRb} and {(Vmax-Eb)(Ra+Rb)/RaRb}.
For quick charging, the charging current should be a current as
high as possible below the less of {(Vmax-Ea)(Ra+Rb)/RaRb} and
{(Vmax-Eb)(Ra+Rb)/RaRb}.
Therefore, in actual current controlling, a current controlling
means should provide a current control range considering the
current controlling accuracy of the means and the target charging
controlling value should be the difference between the current
control range and the less of {(Vmax-Ea)(Ra+Rb)/RaRb} and
{(Vmax-Eb)(Ra+Rb)/RaRb}.
Further, the control means controls the discharging current to be
below the less of {(Ea-Vmin)(Ra+Rb)/RaRb} and
{(Eb-Vmin)(Ra+Rb)/RaRb}.
In other words, the charging/discharging controlling means 105
should control the total current Iall by selecting the less of the
maximum current and the minimum current (maximum and minimum
currents allowed in ratings or in the system) that can flow each of
the storage means 101a and 101b and causing the selected current to
flow respectively through the storage means 101a and 101b.
Similarly, the charging/discharging controlling means 105 should
preferably control the discharging current efficiently to be almost
equal to the maximum capacity of each storage means.
Therefore, similarly to the charging current, in actual current
controlling, a current controlling means should provide a current
control range considering the current controlling accuracy of the
means and the target discharging controlling value should be the
difference between the current control range and the less of
{(Ea-Vmin)(Ra+Rb)/RaRb} and {(Eb-Vmin)(Ra+Rb)/RaRb}.
FIG. 2 is a functional block diagram of the inside of a
charging/disc harging controlling means 105.
In FIG. 2b, the resistances Ra and Rb and the voltages Ea and Eb
that are detected by the status detecting means 104 are sent to the
operation sections 105-1 to 105-3 of the charging/discharging
controlling means 105.
The operation section 105-1 calculates the maximum charging
currents (Vmax-Ea)/Ra and (Vmax-Eb)/Rb of the storage means 101a
and 101b. The operation section 105-3 calculates the maximum
discharging currents (Ea-Vmin)/Ra and (Eb-Vmin)/Rb of the storage
means 101a and 101b. The operation section 105-2 calculates the
ratio of respective currents flowing through the storage means 101a
and 101b to the total current.
The operation section 105-4 calculates the maximum permissible
total charging current Icall from Expressions (5) and (6).
Similarly the operation section 105-5 calculates the maximum
permissible total discharging current Idall from Expressions (7)
and (8).
Receiving the maximum permissible total charging current Icall and
the maximum permissible total discharging current Idall from the
operation sections 105-4 and 105-5, the current control section
105-6 controls the current Iall that flows through the storage
means 101a and 101b.
The current control section 105-6 comprises current control
elements and means to switch on and off these elements to control
the current Iall.
As described above, the first embodiment of this invention can
safely charge and discharge a plurality of parallel-connected
storage means without causing any problem. Simultaneously, this
embodiment enables quick charging, sets discharging currents
effective to the capacities of storage means, and reduces
capacities relative to the discharging currents.
Although the charging/discharging controlling means 105 controls
currents in the above example, the same effects can also be
obtained by controlling voltages or power.
Further, although two storage means 101a and 101b are connected in
parallel in FIG. 2, it is also possible to control the charging or
discharging currents of the storage means even when a plurality of
storage means are connected in series and in parallel by
calculating quantities of status of each storage means such as
impedances and open-circuit voltages and expanding the above
Expressions. This method can charge and discharge storage means
safely and effectively without causing any problem in the storage
means instead of using a current for a single storage means as a
total charging or discharging current.
When a storage means is charging or discharging, however, the
voltage detecting means detects a value including a voltage of the
impedance section, but cannot directly measure the open circuit
voltage E.
It is possible to measure the open circuit voltage E and the
impedance R separately by the following:
FIG. 3 is a graph for explaining an example of process that the
status detecting means executes. In FIG. 3, the vertical axis (Y
axis) represents voltage values and the horizontal axis (X axis)
represents current values. This graph is for explanation only and
not actually plotted in the status detecting means (microcomputer)
104.
The status detecting means 104 receives voltage date measured by
the voltage measuring means 102 and current data measured by the
current measuring means 103 for a preset time period and linearly
approximates these kinds of data by a least-squares method.
The Y intercept of the line is equivalent to the open circuit
voltage E of the storage means 101a or 101b as its X value is 0.
The gradient of the line is equivalent to the impedance R of the
storage means 101a or 101b. This approximate line is expressed by
an equation Y=RI+E.
It is also possible to measure the current I and the voltage V
between the terminals of the storage means 101a or 101b, obtain
their increments (variations) dV and dI in a very short time
period, and directly calculates the impedance from the increments
as follows: R=dV/dI (9)
FIG. 4 is a schematic diagram of a power control apparatus which is
the second embodiment of the invention. This embodiment is an
example of applying the invention to a power charging/discharging
controlling means.
In FIG. 4, a storage means 101a and a current measuring means 103a
are connected in series to each other. A storage means 101b and a
current measuring means 103b are connected in series to each other.
A voltage measuring means 102a is connected in parallel to these
series sets of a storage means and a current measuring means.
Similarly, a storage means 101c and a current measuring means 103c
are connected in series to each other. A storage means 101d and a
current measuring means 103d are connected in series to each other.
A voltage measuring means 102b is connected in parallel to these
series sets of a storage means and a current measuring means.
Further, these two parallel sets of a storage means and a current
measuring means are connected in series to another two parallel
sets of a storage means and a current measuring means. Both ends of
the resulting parallel-series circuit are connected to the
charging/discharging controlling means 105. This
charging/discharging controlling means 105 is connected to a power
supply such as a commercial power supply, a power generator and a
fuel cell and to a load such as an electronic apparatus (which are
not shown in the drawing).
The outputs of the voltage measuring means 102a and 102b and the
current measuring means 103a, 103b, 103c, and 103d are fed to the
status detecting means 104. The outputs of the status detecting
means 104 are fed to the charging/discharging controlling means
105.
In this embodiment, the status detecting means 104 is housed in the
charging/discharging controlling means 105.
The status detecting means 104 calculates the charging status
(quantity of electric charge) of respective storage means 101a to
101d from the detected current and voltage values and determines
the maximum and minimum ones among the charging state values. The
charging/discharging controlling means 105 controls charging of the
storage means by the maximum charging state value and discharging
of the storage means by the minimum charging state value. In
charging/discharging controlling, the charging/discharging
controlling means 105 controls currents, voltages, or power.
By the way, when a plurality of parallel-series connected storage
means are charged, a storage means having the greatest charging
status (quantity of electric charge) completes charging first.
Therefore, the charging/discharging controlling means 105 controls
charging according to the storage means having the greatest
charging status.
Similarly, when a plurality of parallel-series connected storage
means are discharged, a storage means having the smallest charging
status completes discharging first. Therefore, the
charging/discharging controlling means 105 controls discharging
according to the storage means having the smallest charging
status.
Here, the charging status (or state of charge (SOC)) indicates how
much a storage means is charged and the discharging status (or
depth of discharge (DOD)) indicates how much charge a storage means
has to discharge.
The charging and discharging states of the storage means 101a to
101d can be known from their impedances and voltage values. Further
this embodiment causes the status detecting means 104 to detect the
status (such as open circuit voltage) of respective storage means
101a to 101d and controls the charging or discharging currents
according to the quantities of states in the method similar to the
example of FIG. 1. Further, this embodiment controls the
charging/discharging time and so on by the above charging state,
that is, the greatest or smallest charging state value.
This can provide a power storage energy management system that can
charge or discharge series-parallel connected power storage means
safely without causing any problem.
As described above, the second embodiment of this invention can
accomplish the effects similar to those of the first embodiment and
control charging and discharging of respective storage means
according to their charging or discharging status.
FIG. 5 is a schematic diagram of a power control apparatus which is
the third embodiment of the invention. This embodiment is an
example of applying the invention to a power charging/discharging
controlling means.
In FIG. 5, switches 106a and 106b are of the mechanical relay type
or semiconductor element type.
The switch 106a is connected in series to storage means 101a and
101c and a current measuring means 103c. The switch 106b is
connected in series to storage means 101b and 101d and a current
measuring means 103d.
These series sets of switch 106, storage means 101 and current
measuring means 103 are connected in parallel to a
charging/discharging controlling means 105. A voltage measuring
means 102 is connected in parallel to each storage means 101 (e.g.
voltage measuring means 102a to storage means 101a, voltage
measuring means 102b to storage means 101b, voltage measuring means
102b to storage means 101b, and voltage measuring means 102d to
storage means 101d).
The charging/discharging controlling means 105 is connected to a
power supply such as a commercial power supply, a power generator
and a fuel cell and to a load such as an electronic apparatus
(which are not shown in the drawing).
The voltage measuring means 102a to 102d, the current measuring
means 103c, 103d, and switches 106a, 106b are connected to the
status detecting means 104 which is connected to the
charging/discharging controlling means 105.
The status detecting means 104 works to control and detect on/off
status of the switches 106a and 106b. It also detects the status
values of respective storage means 101a to 101d such as internal
impedances, open-circuit voltages, and charging status (remaining
charges and charge quantities).
The charging/discharging controlling means 105 controls
charging/discharging currents, voltages, or powers according to the
on/off status of the switches 106a, 106b, and the status quantities
of the storage means 101a to 101d.
Switches 106a and 106b are used to select or replace storage means
without stopping the power supply. For example, you can replace
either or both of the storage means 102b and 102d by new storage
means by making the switch 106a and opening the switch 106b. These
switches can be used also to disconnect the storage means from a
load or from the charging/discharging controlling means 105.
Also when the storage means 101a to 101d are disconnected from the
switch 106a or 106b, the voltage measuring means 102a to 102d can
send the detected values normally to the status detecting means
104.
Therefore if the charging/discharging controlling means 105 charges
or discharges a storage means without knowing that a switch 106a or
106b is open, the storage means connected to the
charging/discharging controlling means 105 may be disturbed. To
prevent this, the third embodiment of this invention detects the
on/off status of the switches 106a to 106b.
The other actions and functions of the third embodiment are similar
to those of the first embodiment.
As described above, the third embodiment of this invention can
accomplish the effects similar to those of the first embodiment
even when switches are connected in series to the storage
means.
FIG. 6 is a schematic diagram of a power control apparatus which is
the fourth embodiment of the invention. This embodiment is an
example of applying the invention to a power charging/discharging
controlling means.
In FIG. 6, a load 107 is a generic part such as an electronic
apparatus to which a power supply apparatus supplies power.
Voltage measuring means 102a and 102b are respectively connected in
parallel to the storage means 101a and 101b as shown in FIG. 6.
Further, current measuring means 103a and 103b are respectively
connected in series to the storage means 101a and 101b.
A load 107 and a charging/discharging controlling means 105a
connected in parallel to the storage means 101a.
Charging/discharging controlling means 105a and 105b are connected
in parallel to the storage means 101b. This charging/discharging
controlling means 105b is connected to a power supply such as a
commercial power supply, a power generator and a fuel cell and to a
load such as an electronic apparatus (which are not shown in the
drawing).
Further, a status detecting means 104a is connected to the voltage
measuring means 102a and a current measuring means 103a. A status
detecting means 104b is connected to the voltage measuring means
102b and a current measuring means 103b.
The status detecting means 104a is housed in the
charging/discharging controlling means 105a and the status
detecting means 104b is housed in the charging/discharging
controlling means 105b. The charging/discharging controlling means
105a and 105b are so configured to transfer their current control
signals and storage-means status values to and from each other.
The purpose of this configuration is to enable the
charging/discharging means 101a and 101b to cooperate or separately
work to supply power to the load 107 or the other electronic
apparatus.
The other operations and functions of the status detecting means
104a and 104b and the charging/discharging controlling means 105a
and 105b are similar to those of the first embodiment of FIG.
1.
As described above, the fourth embodiment of this invention can
accomplish the effects similar to those of the first embodiment.
Additionally this embodiment enables connection of multiple storage
means and multiple charging/discharging means and enables the
charging/discharging means to share state quantity data of the
storage means and information of respective charging/discharging
means. With this, the power control apparatus can control charging
and discharging current, voltages, or powers of the
charging/discharging means according to the status quantities of
storage means and thus utilize the storage means.
FIG. 7 is a schematic diagram of a power control apparatus which is
the fifth embodiment of the invention. This embodiment is an
example of applying the invention to a storage-means energy
management system.
In FIG. 7, the storage-means energy management system contains a
commercial power supply 108, a solar energy generator 109, power
supply switches 110a to 110e, and a fuel cell apparatus 114.
A charging/discharging controlling means 105 is connected to the
commercial power supply 108, the solar energy generator 109, the
fuel cell apparatus 114, and the load apparatus 107 through the
power supply switches 110a to 110e.
The fuel cell apparatus 114, the solar energy generator 109, the
load apparatus 107, the power supply switches 110a to 110e, and the
MCU of the charging/discharging controlling means 105 are
interconnected with two-way communication systems. The output
signals of the status detecting means 104 are fed to the MCU of the
charging/discharging controlling means 105.
The fuel cell apparatus 114 produces electric energy by oxidative
reaction of oxygen (in air) and hydrogen gas stored in container or
hydrogen gas obtained by modifying gasoline or methanol and outputs
a.c. power through a converter or the like.
The solar energy generator 109 photo-electrically converts solar
light into d.c. power by solar cells and outputs a.c. power through
a converter or the like.
The load apparatus 107 generically represents home electric
appliances (e.g. an electric/electronic apparatus such as air
conditioner, refrigerator, microwave oven, and lamps) and electric
equipment (e.g. motor, elevator, personal computer, and medical
apparatus).
The load apparatus 107 may contain a switch 110 in it.
The storage means 101a to 101d, the voltage measuring means 102a to
102d, and the current measuring means 103c and 103d are connected
in a configuration similar to that of the embodiment of FIG. 5
(excluding switches 106a and 106b).
The MCU controls charging and discharging of the storage means 101a
to 101d by controlling a current control circuit comprising of
transistors (TR1 to TR6), diodes (D1 to D6), resistors (R1 and R2),
a capacitor (C), and coils (L1 and L2) according to status
detection signals sent from the status detecting means 104 which
has a function similar to that of the embodiment of FIG. 5.
The embodiment of FIG. 7 normally supplies required power to the
load apparatus 107 from the commercial power supply 108, the solar
energy generator 109, and the fuel cell apparatus 114.
When detecting that power from the commercial power supply 108, the
solar energy generator 109, and the fuel cell apparatus 114 is not
enough, the MCU supplies power to the load apparatus 107 from the
storage means 101a to 101d through the charging/discharging
controlling means 105.
When detecting that power from the commercial power supply 108, the
solar energy generator 109, and the fuel cell apparatus 114 is
excessive, the MCU charges the storage means 101a to 101d through
the charging/discharging controlling means 105.
In the above operation, the status detecting means 104 detects the
status of respective storage means 101a to 101d. Judging from these
status values, the MCU determines currents, voltages, and power
required by the commercial power supply 108, the solar energy
generator 109, the fuel cell apparatus 114, and the load apparatus
107. The charging/discharging controlling means 105 controls the
charging or discharging currents, voltages, and power required by
them.
As described above, the fifth embodiment of this invention can
accomplish the effects similar to those of the first
embodiment.
As the fifth embodiment can quickly charge storage means and obtain
great discharging currents relative to the storage capacity without
causing any problem, it can reduce the contract demand and power
consumption of the commercial power supply 108 and the rated power
generation of the solar energy generator 109 and the fuel cell
apparatus 114. This can reduce charging means costs, equipment
expenses, and running costs.
This embodiment can ease concentration of power consumption and
even out the power consumption by supplying power to the commercial
power supply 108 from the storage means when a power consumption
concentrates on a certain period and charging the storage means
when a power consumption is less.
The energy management system for storage means stated in the fifth
embodiment of this invention can take a configuration other than
the illustrated one.
The fifth embodiment is applicable to production plants, building
systems, general households, and so on.
FIG. 8 is a schematic diagram of a power control apparatus which is
the sixth embodiment of the invention. This embodiment is an
example of applying the invention to a storage-means energy
management system, particularly to railway vehicles, automobiles,
and so on.
In FIG. 8, the storage-means energy management system contains a
low-potential load apparatus 111, a high-potential load apparatus
112, and a motor generator 113.
The motor generator 113 is connected to a charging/discharging
controlling means 105b which is functionally similar to that in the
storage-means energy management system of FIG. 7.
The storage means (101a and 101b), the voltage measuring means
(102a and 102b), the current measuring means (103a and 103b), the
status detecting means (104a and 104b), and the
charging/discharging controlling means 105 are configured similarly
to that of FIG. 6, but the status detecting means 104b is not
housed in the charging/discharging controlling means 105b.
In the embodiment of FIG. 8, the high-potential load apparatus 112
is connected to the charging/discharging controlling means 105b
(configuration similar to that of FIG. 8) on the storage means 101b
side through the charging/discharging controlling means 105c
(configuration similar to the charging/discharging controlling
means 105b). The low-potential load apparatus 111 connected to the
storage means 101a.
The motor generator 113 works to start the engine (internal
combustion engine), assist the driving force of the engine
(powering), and generate power (regeneration). During powering, the
motor generator 113 receives power from the storage means 101a and
101b. During regeneration, the motor generator 113 supplies power
to the storage means 101a and 101b.
The low-potential load apparatus 111 are electric loads and other
power supply units of rated voltages from some volts to 42 volts
such as solenoid valves of the engine and audio sets.
The high-potential load apparatus 112 are electric loads having
rated voltages of some hundred volts such as lamps and an air
conditioner.
Also in this embodiment, the status detecting means 104a and 104b
detect the status of respective storage means 101a and 101b. The
charging/discharging controlling means 105b controls charging or
discharging currents, voltages, and powers according to the
detected status quantities considering the I/O requests of the
motor generator 113, the low-potential load apparatus 111, and the
high-potential load apparatus 112.
This embodiment enables the charging/discharging means (105a to
105c) to share state quantity data of the storage means (101a, 101b
and 101c) and information of respective charging/discharging means
(105a, 105b, and 105c) and thus utilizes the storage means.
As described above, the sixth embodiment of this invention can
accomplish the effects similar to those of the first
embodiment.
When applied to a tracked vehicle such as electric car, hybrid
electric car, railway car, and mono-rail car, the power storage
energy management system which is the sixth embodiment of this
invention can reduce the charging time and the weight of the
storage means. Therefore, this system can assist engine torques at
the startup of the engine, convert kinetic energy of braking into
electric power, and store the regenerated power, which leads to
reduction of shipping cost of the system and maintenance
frequency.
Although the above embodiment is an example of applying a power
control apparatus of this invention to a charging/discharging
controlling means, this invention can also be applied to a charging
controlling apparatus and a discharging controlling apparatus.
In other words, when applied to a charging controlling apparatus,
the power control apparatus calculates the internal impedance of
each storage means from the detected current and voltage and
controls the charging current to satisfy Expressions (5) and
(6).
When applied to a discharging controlling apparatus, the power
control apparatus calculates the internal impedance of each storage
means from the detected current and voltage and controls the
discharging current to satisfy Expressions (7) and (8).
Further, as the embodiments of this invention can calculate the
internal impedance of respective storage means, it is possible to
estimate the service life of each storage means from its impedance
value. This estimation is carried out by the current controlling
section 105f in FIG. 2.
Therefore, it is possible to show the service life and the expected
replacement time of each storage means.
This invention can provide a power control apparatus that can
control charging and discharging of a plurality of storage means
without causing any problem while reducing the charging periods and
capacities relative to the discharging current values.
Although the present invention has been illustrated and described
with respect to exemplary embodiment thereof, it should be
understood by those skilled in the art that the foregoing and
various other changes, omission and additions may be made therein
and thereto, without departing from the spirit and scope of the
present invention. Therefore, the present invention should not be
understood as limited to the specific embodiment set out above but
to include all possible embodiments which can be embodied within a
scope encompassed and equivalent thereof with respect to the
feature set out in the appended claims.
* * * * *